It is a common used technique for increasing engine efficiency and performance to cool heat exposed components of rotary flow machines. Especially cooling of turbine blades in gas or steam turbo engines is of high importance to operate such turbines at higher temperatures than would be permissible with uncooled turbine blades.
A well known cooling technique for the rotating blades in a rotary flow machine is based on feeding the blades via the rotating unit providing internal cooling channels which are indirectly or directly fluidly connected with a cooling channel system inside the blades.
U.S. Pat. No. 4,178,129 discloses a gas turbine engine cooling system in which each blade roots is provided with individual pitot receivers which collect a portion of a cooling flow supplied from an annular array of pre-swirl nozzles, which have a circumferentially continuous outlet flow area and direct said cooling flow into a portion only of the interior of the blade, preferably adjacent the leading edge.
Another cooling arrangement for a bladed rotary in a gas turbine engine is disclosed in U.S. Pat. No. 5,984,636. Each of the blades includes cooling air passages and a cover with curved fins mounted adjacent to but connected to the rotor and spaced apart slightly from the rotor disc to form a passage way for the cooling fluid. The cavity which is bordered by the cover and the rotor disc is fed on a relative low radius and the pressure rise is achieved with vanes working like a radial compressor. Complicated design making a separate part attached to the rotor necessary.
A multitude of further solutions are well known for feeding blades with cooling air via rotor bores, these solutions however might cause life time problems because if there is not enough space for feeding cooling air into the rotating blades pressure will rise and might not be sufficient finally.